This invention applies to the field of fiber optics, and more particularly to narrow-beam spotlight luminaires, known as "pinspot" or "follow-spot" lights that produce a well collimated distribution of light with virtually no light outside an intense central beam; and wherein the beam may be zoomed to larger diameters.
Presently known fiber optic light spotlights normally use a collimating lens with the emitting end of the light guide at the focus of the lens. The emitted beam from the fiber optics light guide has a wide photometric distribution exceeding a 70.degree. included conical angle. In order to intercept all the emitted rays from the light guide, the lens must be very large in diameter and have a very short focal length. This produces a beam having a very sharp and harsh image of the individual fiber ends, interstices and discontinuities of the fiber optic light guide. The extreme degree of refraction of a simple short focal length lens produces a halo of chromatic aberration around the projected beam. In prior art lighting applications these characteristics are aesthetically objectionable, butthere are no available alternatives.
Zooming of presently-known fiber optics spotlights is very limited, in that movement of the light source away from the focal plane of the lens produces a hollow beam with a dark spot in the center. Although this could be overcome with multiple, differentially-moved lenses (as in camera zoom lenses) that structure is too complex and costly for lighting purposes. Dimming of a zoom fiber optics spotlight is presently believed to be unknown in the prior art.
The primary purpose of the present invention is to provide a fiber optic light guide luminaire having narrow-beam zoomable to a uniformly illuminated wide beam; using a simple, inexpensive lens, in which the beam is free of a harsh edges, fiber images and chromatic aberrations; and which may be dimmed over the full range of zoomed beam widths.